This invention relates generally to the field of cast removable partial dentures and, in particular, to an improved technique for removing a master dental cast from an impression material-containing, duplication flask.
Laboratory techniques used in the fabrication of partial dental casts are generally accomplished by means of a reversible hydrocolloid impression material. Naturally, when a partial denture is indicated, the dentist will first have a negative impression of the oral cavity made by the insertion in the patient's mouth of a dental impression tray. The negative impression thus made is poured with a suitable dental stone material and allowed to set a specified time to thereby produce a positive impression that may be used as a master dental cast. Thereafter, by placing this master cast in a duplicating flask and filling with a suitble hydrocolloid material, for example, a new negative impression duplicating the previously obtained impression of the oral cavity now found in the master cast may be achieved.
Under present methods, the master dental cast is removed from the hydrocolloid impression material in the duplicating flask by any of several means to include the use of a pair of sharp instruments or, in some cases, even the fingers of the human hand to grip the cast in an oppositely-disposed relation around the circumference thereof to thus lift the cast from the impression material. With such techniques, however, it is practically impossible to remove the dental cast without imposing some adverse stresses on the impression material. It is known that such adverse stresses result in an inaccurate cast and, although dentists, dental laboratory technicians and patients have been forced to live with this situation for the want of a better solution, it is quite evident that such a situation is not a desirable one. This led to the development of the novel means of the present invention which, as will readily appear hereinafter in the following summary and detailed description, solves or substantially solves the aforementioned problem of adverse stress in a new, improved and yet relatively simplified manner.